Linker error when passing tuple to object constructor

[sztomi]

Using the latest release (2.1.5), consider the following code:

#include <iostream>
#include <tuple>

#include <msgpack.hpp>

int main() {
    msgpack::object obj(std::make_tuple(2, "hello", 3.4));
    std::cout << obj << "\n";
    return 0;
}

This code compiles, but does not link:

Undefined symbols for architecture x86_64:
  "msgpack::v1::adaptor::object<std::__1::tuple<int, char const*, double>, void>::operator()(msgpack::v2::object&, std::__1::tuple<int, char const*, double> const&)const", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

If I change the first line to msgpack::object obj(123); it compiles and links correctly. I would expect the tuple to also link correctly.

OS, compiler info:

macOS 10.12.6
Apple LLVM version 8.1.0 (clang-802.0.42)

[redboltz]

@sztomi , std::tuple is mapped to ARRAY. ARRAY requires msgpack::zone.
See https://github.com/msgpack/msgpack-c/wiki/v2_0_cpp_object

So, you can use msgpack::object with msgpack::zone as follows:
https://wandbox.org/permlink/a4V243pj4WYDAuyX

I think that compile error is better than link error, but so far, it makes link error.

[sztomi]

Can I use zone with the pack function?

[sztomi]

To shed some light on what I'm trying to do:

This is a function that produces a msgpack::unpacked for use in unit tests. I know it's not efficient, but that's not a problem for unit tests. This used to work with older versions, but now that I'm upgrading, I'm getting a linker error.

template <typename... Types>
inline msgpack::unpacked make_unpacked(Types... items) {
    auto obj = std::make_tuple(items...);
    msgpack::sbuffer buf;
    msgpack::pack(buf, obj);
    return msgpack::unpack(buf.data(), buf.size());
}

// called as:

    auto o = make_unpacked(3, 42, "foo", "bar");

This used to work with older versions, but now that I'm upgrading, I'm getting a linker error. How can I safely make an unpacked out of a tuple?

[redboltz]

I think that your code should work.
See
https://wandbox.org/permlink/56ZuoHJ1Nb7JRK3i

[sztomi]

You are right. Sorry, linker errors are confusing sometimes. My actual error:

"std::__1::enable_if<!(is_array<msgpack::v1::type::nil_t>::value), void>::type msgpack::v1::operator<<<msgpack::v1::type::nil_t>(msgpack::v2::object&, msgpack::v1::type::nil_t const&)", referenced from:
      msgpack::v1::adaptor::object_with_zone<msgpack::v1::type::nil_t, void>::operator()(msgpack::v1::object::with_zone&, msgpack::v1::type::nil_t) const in dispatcher_test.cc.o
      msgpack::v2::object::object<msgpack::v1::type::nil_t>(msgpack::v1::type::nil_t const&) in librpc.a(response.cc.o)
  "void msgpack::v1::operator<<<char, 4ul>(msgpack::v2::object&, char const (&) [4ul])", referenced from:
      msgpack::v2::object::object<char [4]>(char const (&) [4]) in response_test.cc.o

And the code that uses it:

    auto o = make_unpacked(3, 42, "foo", "bar");
    response r(std::move(o));

And that constructor:

    using response_type =
        std::tuple<uint32_t, uint32_t, msgpack::object, msgpack::object>;

response::response(msgpack::object_handle o) : response() {
    response_type r;
    o.get().convert(r);
    id_ = std::get<1>(r);
    auto &&error_obj = std::get<2>(r);
    if (error_obj != msgpack::type::nil_t()) {
        error_ = std::make_shared<msgpack::object_handle>();
        error_->set(msgpack::clone(error_obj).get());
    }
    result_ = std::make_shared<msgpack::object_handle>(
        std::get<3>(r), std::move(o.zone()));
}

When upgrading, I had to change convert(&r) to convert(r) and error_->assign(msgpack::clone(error_obj)) was changed to error_->set(msgpack::clone(error_obj).get());

Any clue what could cause the linker error? The make_unpacked function did not change.

[redboltz]

I don't understand the code above. Could you show me a minimal and complete code that reproduces the error?

If

#include <iostream>
#include <tuple>

#include <msgpack.hpp>

int main() {
    msgpack::object obj(std::make_tuple(2, "hello", 3.4));
    std::cout << obj << "\n";
    return 0;
}

is so, you can use zone as I mentioned.

[d223chen]

I had a similar issue when trying to create a msgpack::object with a Struct for which I had an adaptor.

My initialization was initially like:
msgpack::object obj(myClass()).

After adding the zone argument, like so

   #include <iostream>
   #include <tuple>
   #include <string>

   #include <msgpack.hpp>

   class myClass{
     int typeId;
     std::string header;
     int timestamp;
     MSGPACK_DEFINE(typeId, header, timestamp); //value array
   };

   int main() {
     msgpack::zone z;
     msgpack::object obj(myClass(), z);
     std::cout << obj << "\n";
     return 0;
   }

it worked!

I had a similar linker error to sztomi which made debugging it really difficult. Of course from the documentation for msgpack::object it is clear that a zone must be used with a complex object type (since we are not using a msgpack::object_handle and thus must be responsible for the memory management).

Perhaps this can be investigated further on the topic of issuing a better compiler error?